Machines for the production of reels of crepe paper, smooth paper and other light-weight web materials such as nonwoven fabrics, are known to comprise a so-called “winder” apparatus, which makes it possible to form reels of materials having a preset diameter and comprising a tubular core, usually named “rod” or “spool” onto which the material is wound upon forming each reel. The winder is essentially made up of a motorized cylinder with horizontal axis. The winding of the material during the formation of the reel is ensured by keeping the latter in contact with the surface of said cylinder: the axis of rotation of the reel, that is, of the respective rod, is parallel to the axis of rotation of the winding cylinder. To allow a continuous contact between the winding cylinder and the reel in the course of formation, that is, the “growing” reel, the rod of the latter is engaged to corresponding supports which are mounted horizontally movable on a support structure facing the material-feeding area. Upon completion of a reel, provision is made for moving it away and replacing it with an unloaded rod that is, with a spool. This is previously driven into rotation about its longitudinal axis, so that the peripheral speed of any surface point thereof is equal to the material-feeding speed. To this end, the unloaded rod is supported by two arms located at the two ends of the winding cylinder and movable from and to the area immediately downstream of the same cylinder. When replacing a reel, the arms move the unloaded rod from a position overhanging the winding cylinder to a position of surface contact with the same cylinder, and the unloaded rod is driven into rotation. When the material begins winding up over the thus positioned rod, the arms move the latter to the position previously taken by the just completed reel which is moved away from its position, and the paper web breaks the moment it begins winding up over the new rod.
Upon the replacement of a reel it is possible that the web fails winding up on the unloaded rod, so that the formation of the reel is to be interrupted to start again the winding operation. This has a consequent loss of production and considerable economic damages; moreover, the replacement operation is largely dependent on the skill of the operator in the charge thereof.